1. Field of the Invention
This invention relates to a gaseous flow construction of a large-sized box member for refrigerated transportation and a box member using the same, by which large quantities of perishables such as vegetables, fruits, fishes and meats are transported without decreasing freshness thereof.
2. Prior Art
When, for example, vegetable perishables such as vegetables, fruits and flowers or animal perishables such as fishes and meats are transported, it is most important not to decrease freshness of the perishables during transportation and storage.
Moreover, a condition for preserving freshness of the perishables is considerably different depending on the types of the perishables transported.
Accordingly, in order to preserve freshness of perishables, it is necessary to keep them under an optimum low temperature condition in accordance with the type of the perishables.
For instance, perishables such as vegetables, fruits and flowers would require a range of low temperature within which deterioration troubles due to a low temperature would not be invited.
In the case of the perishables such as fishes and meats, if changes in taste and preservability would occur due to freezing, at least a range of non-freezing low temperature condition would be required for preserving them. On the other hand, in the case of the fishes and meats which would not invite a problem of taste change even when they would be frozen, a low temperature condition different from the above would be selected correspondingly.
In the case of a large-sized box member for refrigerated transportation, for example one for transporting a large quantity of perishables keeping freshness to a remote destination such as an overseas destination, the total length is determined by the international standards, and in general a length of 20 feet (about 6 m) or 40 feet (about 12 m) is widely used.
It is a common practice that an evaporator, a blast fan, a humidifying means and the like for a refrigeration unit are provided at the forward end portion of the inner side of the box member. In this case, even in the overseas container of 20 feet, the rear end portion of the inside thereof is at least spaced apart 5 m or more from the refrigerating unit. Furthermore, cool air in the box member would not be uniformly distributed depending on the loading condition of goods. Thus, the condition of the air should naturally be different from a position close to the refrigeration unit to a position remote therefrom. Further, in the overseas container of 40 feet, the rear end thereof would be spaced 10 m or more from the refrigerating unit and moreover an opening door would be mounted to the rear end thereof, whereby, when the door is opened, hot air would rapidly flow from the outside, so that it would not easy to keep the air condition uniformly at every position in the box member.
The above described situation would not only be limited to the overseas container and it would true of a large sized land container for land transportation by a large sized truck.
As described above, in order to keep freshness of the perishables, it is necessary to preserve the perishables at the optimum low temperature condition depending on the types thereof, so that, in the past, in order to transport the perishables, there has been proposed a humidity control device of a refrigerating unit as disclosed in Japanese Utility Model Unexamined Publication No. 63-63671 for example.
This conventional humidity control device of the refrigerating container is constructed such that, in addition to a refrigerating unit for feeding the air cooled by a refrigerator, a humidifying means is provided. This humidifying means is controlled in accordance with a signal from a humidity detecting means which detects humidity of air in a box member. Main and auxiliary flow paths of cooled air are laid on a floor of the box member, and it is said that cooled air adjusted in temperature and humidity is distributed from clearances of the flow paths or holes opened upwardly in these flow paths to the every corners through gaps between the perishables loaded in the box member, so that the box member can be uniformly cooled.
With the above-described conventional construction, in order to keep a uniform temperature and also humidity in the box, the cooled air is fed from below to above through the clearance or the open hole of the flow paths.
However, as the goods would be piled up on the main air flow path and the auxiliary air flow path, when the undersurfaces of the goods is close to flat surfaces without irregularities, the clearances or open holes of the flow paths would be substantially completely blocked, thus presenting a problem that the air would not flow upwards and not distributed to the corners of the goods.
Furthermore, in general, a heating device would be provided in a refrigerating unit, and the heating device would be periodically operated to defrost inside the refrigerating unit while a blast fan is stopped. However in that case, in the refrigerating unit having a humidity control means, frosting would be accelerated in particular, and, even if the blast fan is stopped during defrosting, heated hot air would flow into the box member due to natural convection, thus presenting a problem that the temperature in the box member would not be uniform.
Further, in the case of the conventional refrigerating unit, when the door at the rear end would be opened due to loading or unloading of the goods to and from the box member, hot air would rapidly flow into from the outside, thus presenting a problem that the air condition in the box member would not be kept constantly.
Furthermore, in the conventional construction, as the humidifying means is controlled in response to the signal from the humidity detecting means, the construction of the humidifying means is highly complicated. And the water level of a water tank supplying the water to the humidifying means would not be easily confirmed from the outside, thus presenting a problem that water supply would not be easy.